Ballpoint pen

Abstract

A ballpoint pen. In the ballpoint pen, an oil-based ballpoint pen ink composition has an ink viscosity with a range of 500 mPa·s to 15000 mPa·s inclusive at 20° C. and a shear rate of 500 sec −1 . A ball has a ball diameter of 0.5 mm or less. A tip distal end portion includes a first swaged portion and a second swaged portion. The first swaged portion has an inclination angle with a range of 90 degrees to 100 degrees inclusive. The second swaged portion is provided closer to a distal end side of a ballpoint pen tip than the first swaged portion and has an inclination angle with a range of 110 degrees to 130 degrees inclusive. An angle of a bottom wall of a ball holding chamber is the same as the inclination angle of the second swaged portion.

The invention claimed is: 
     
       1. A ballpoint pen comprising a ballpoint pen refill, the ballpoint pen refill including an ink reservoir cylinder and a ballpoint pen tip, an inside of the ink reservoir cylinder being filled with an oil-based ballpoint pen ink composition, the ballpoint pen tip being attached to a distal end portion of the ink reservoir cylinder, wherein
 a tip main body of the ballpoint pen tip includes:
 a ball holding chamber that holds a ball in a manner of allowing the ball to rotate while causing a part of the ball to protrude from a tip distal end portion; 
 a ball socket provided on a bottom wall of the ball holding chamber, the ball being placed on the ball socket, the ball socket having a circular-arc surface conforming to an outer shape of the ball; 
 an ink distribution hole formed in a center of the bottom wall of the ball holding chamber; and 
 a plurality of ink distribution channels radially extending from the ink distribution hole, 
 
 the oil-based ballpoint pen ink composition has an ink viscosity with a range of 500 mPa·s to 15000 mPa·s inclusive at 20° C. and a shear rate of 500 sec −1 , 
 the ball has a ball diameter of 0.5 mm or less, 
 a sealing surface with a circular-arc shape is formed on an inner wall of the tip distal end portion, 
 the tip distal end portion includes
 a first swaged portion having an inclination angle with a range of 90 degrees to 100 degrees inclusive, and 
 a second swaged portion provided closer to a distal end side of the ballpoint pen tip than the first swaged portion, the second swaged portion having an inclination angle with a range of 110 degrees to 130 degrees inclusive, and 
 
 an angle of the bottom wall of the ball holding chamber is the same as the inclination angle of the second swaged portion. 
 
     
     
       2. The ballpoint pen according to  claim 1 , further comprising a coil spring that presses the ball toward the distal end side of the ball point pen tip, wherein a pressing load of the coil spring is in a range of 5 gf to 10 gf inclusive. 
     
     
       3. The ballpoint pen according to  claim 1 , wherein the oil-based ballpoint pen ink composition contains a colorant, an organic solvent, a saturated fatty acid, and a phosphoric acid ester, the phosphoric acid ester having C 1 H 22H-1 O—C 2 H 4 O or C m H 2m+1 O (1, m=1 to 30 inclusive). 
     
     
       4. The ballpoint pen according to  claim 3 , wherein the number of carbon atoms of the saturated fatty acid is in a range of 10 to 20 inclusive. 
     
     
       5. The ballpoint pen according to  claim 3 , wherein carbon chains (1, m) of a terminal alkyl group of the phosphoric acid ester are in a range of 1 to 15 inclusive. 
     
     
       6. The ballpoint pen according to  claim 3 , wherein the oil-based ballpoint pen ink composition contains a ketone resin or a polyvinyl butyral resin. 
     
     
       7. The ballpoint pen according to  claim 3 , wherein the colorant is a pigment or a salt-forming dye.